I thought I would take the time to ask you knowledgable U2 fans about the unreleased and other b-side material that is in the box set. I am familiar with every studio album, but I don't know anything about the other stuff... Many people talk about "passengers" or "MDH" and I, along with others I'm sure, have no idea what these are. And the significance of the 2 concerts on there, I get that one of them is from new year's day, but what about the others?